Investigatory methods for material characterisation are referred to as thermal analysis, wherein the sample is subjected to a controlled temperature program. Dimensional changes, mass changes, calorific effects, the specific thermal capacity and escaping gases, for example, are investigated.
The samples may oxidise due to residual oxygen in an otherwise inert gas atmosphere provided in the sample space, which can falsify the results and is therefore undesirable. The presence of residual oxygen in the inert gas, which is also referred to and/or used as purging gas, in apparatus for measurements under a nominal inert gas atmosphere (e.g. nitrogen, argon or helium) therefore represents a problem.
Residual oxygen in an apparatus is usually minimised by the fact that the typically vacuum-tight apparatus is evacuated and then filled and purged with inert gas of high purity. The residual oxygen concentration thus depends on the vacuum tightness of the apparatus, the vacuum tightness of the gas supply lines and the purity of the inert gas present. Purification of the purging gas before entry into the apparatus is just inadequate due to the finite leakage rate of the apparatus itself and the desorption of residual oxygen from the walls of the apparatus.
Accordingly, although devices and methods for removing residual oxygen from an inert gas according to publications DE 2 340 102 A, DE 698 30 247 T2, DE 36 21 014 C2 and DE 689 10 638 T2 are suitable in principle for reducing the residual oxygen content of an inert gas, the purity of the inert gas in respect of residual oxygen in each case deteriorates again before the use of the inert gas due to its subsequent path into respective apparatuses. In certain production processes and production environments, such as are used for example as applications for inert gas in the aforementioned publications, this may possibly be acceptable, but satisfactory results are not thereby obtained for measurement and analysis apparatuses and methods, such as in particular thermal analysis apparatuses and methods.